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Sleeve | Concrete poured | Complete
LNA+Relay | LNA Int | Feed Cage | Actuator | Scissor Jack
Copper Heat Spreaders |75W Amp |300W Amp Construction
VA3TO 23cm EME station details:
Transceiver: Kenwood TS-2000X w/ split RX & TX ports.
Dish: 7.5 foot (2.3m) TVRO dish, 0.35 f/d, modified polar mount.
Feedhorn: VE4MA circular feedhorn.
Amplifier: Homebrew 75W (~65w @ feed) SSPA - 1x XRF286 on W6PQL pcb. (300w SSPA under construction)
LNA: G4DDK Dual Stage VLNA kit.. Gain = ~35dB, NF = <0.35dB.
Feedline: 35' of 7/8" LDF-5 Hardline on TX, FSJ4-50 Superflex on RX.
Transition cables: FSJ4-50 Superflex.
Isolation Relay: Relcomm RDL-SR012.
Operator: Hugh Duff
Location: Waterdown, Ontario, Canada. 40 kM NW of Niagara Falls.
BITTEN BY THE EME BUG !
After getting a taste for EME operation using a modest station on the 2m band I'm hooked. The limitations of my small antenna array were realized so I decided to try EME on one of the microwave bands using a dish. The dish could be mounted just above the ground in my backyard, not too obtrusive or offensive to the nieghbors, and easily serviced. I would have a limited view of the sky due to the proximity of my and neighboring homes but there would be a big enough window to work most of the world when the declination of the moon is high. The 23cm (1.2 GHz) band seemed like the obvious choice since it is the gateway to the microwaves within the amateur radio spectrum. It's also the 2nd most popular EME band with plenty of active stations so it offers a good yield of potential contacts for the required equipment and effort.
In the summer of 2008 I did some research and started acquiring the necessary components to assemble a 23cm EME station. A 2.3 metre TVRO dish was offered to me by a local ham at the cost of gas for delivery, so I took him up on it. With autumn fast approaching the next order of buisness was to get the dish mounted before the ground froze. Our backyard is small but well used by the family through the summer so I needed an installation that could be set up and dismantled for seasonal use. I came up with a scheme that would leave little trace of the dish during the "off season". A sleeve with bottom plate that resembles a 2.5 foot deep cup was fabricated. The sleeve is the next size up to the OD of the mast so the mast will telescope into it. A hole was dug and the cup was set in concrete. The top of the mast mount is just below grade so the hole can be covered when the dish is removed. A slot at the top of the sleeve and a 1/2" rod through the mast form a key to prevent it from turning.
Work on the dish and mount was carried out in my garage as winter arrived. A few trips were made to the local Metal Supermarket and Home Depot for raw materials and stainless hardware. I spent a good bit of time fabricating the feedhorn mount which is a close copy of one made by Dave, WW2R per pictures on his web site. Dimensions of the feed mount were approximated using Dave's pictures and finalized by taking physical measurements of my dish feed support arms and the feedhorn. The beauty of this "cage" approach is that it's fully adjustable allowing the feedhorn to be centred and tilted if necessary for perfect alignment. And by design it can accomodate a smaller feedhorn should I opt to try EME on a higher microwave band. (13cm EME is already on my mind, but not to get ahead of myself.) The original TVRO dish mount had to be modified to provide adjustable declination. This was handled by employing a car scissor jack, per pictures on the G4DDK and WW2R web sites. Several modification pieces were fabricated then my neighbor who is a welder by trade was kind enough to weld up the parts for me. With the majority of the bulky mechanical work done the radio was then modified for split RX & TX on 23cm, the LNA was built & tested and work on the solid state power amplifier began.
On February 01, 2009 I heard my first 23cm signals off the moon using the small dish. I copied several CW (Morse Code) stations and marginally heard a Single SideBand (voice) contact in progress which I had never had the joy of experiencing on 2m. I also decoded a few stations calling CQ in JT65C digital mode.
The following weekend on February 07,2009 during the 23cm SSB Contest I heard more voice signals. One of them was OE9ERC in Austria which I managed to record. Click here OE9ERC@VA3TO.Wave to listen to it. The reception is very light (2x2 ?) so it took a couple of sequences for me to get the full callsign. This certainly won't impress any HF operator who is used to 5x9 signals on 20 metres but it is a feat in the circles of weak signal operation. Hearing voice off the moon was simply impossible using my 2m EME setup so I'm impressed !
My initial observations after listening to some 23cm EME signals for the fist time are; The lack of fading due to Faraday rotation through the use of circular polarization. This is a huge advantage as I've wasted an accumulation of many hours waiting for the polarity to align or "come back around" while using linear polarization on 2m. Also very notable is the lower atmopspheric noise level which is quite a contrast to the normal hiss heard on the lower bands. The wide range of varying conditions & propagation throughout the radio spectrum keeps the romance of radio alive for me.
First Contacts !
On March 01, 2009 I made my fist two 23cm EME contacts using WSJT. The big amplifier is still under construction so I lashed up the 75w driver amp and worked G4CCH and PA3FXB for initials #1 and #2.. I copied both stations 'O' with signals of -15dB and -18dB respectively. Thanks to Howard and Jan for the thrill and congratulations on their big signals.
The next weekend (Mar.07 & 08) brought my first CW initial with K2UYH plus JT65 contacts #3 K2UYH and #4 DJ9YW ! These contacts were made with the LNA in the shack while I'm sorting out a sequencing problem that keeps taking out the first amp in the LNA.
- March 01/09: First amp in LNA (ATF-36077) blown for the 3rd time. Sequencer appears to be working and LNA should be able to handle theoretical power seen at the input. ...Headscratcher.
- March 13/09: Took isolation relay to work and measured port isolation on network analyzer. Specified for >80dB @ 1GHz., measured 75dB @ 1.3 GHz. Return loss good at -35dB.
- March 15/09: Brought a spectrum analyzer home from work for the weekend to take some isolation measurements. With the LNA removed, isolation relay at the feed energized and 80w (+49dBm) applied to TX port I measure -18dBm on the shack end of the RX feedline which is higher than calculated isolation but still low enough not to exceed the +10dBm input limit of the PHEMT. Also measured cross pol isolation of the feed (RX feedline connected to RX probe at feedhorn via isolation relay), I saw +24dBm which is about right (25dB isolation) but that would most certainly blow the PHEMT. Then I connected the LNA in the shack and manually switched the isolation relay, PA bias on, TX power applied for a few seconds then reversed the sequence. Did this a few times and the LNA survived so I have to assume that my problem with the blown PHEMT is related to sequencing. Still a little concerned that the isolation through the relay is nowhere near the rated 80dB. Plan to add a second isolation relay.
- March 25/09: Installed 2 isolation relays and put LNA back at feedhorn. All seems well... LNA survived many RX-TX-RX test cycles. Declination is still to the South and tomorrow is a new moon so I need to wait for a few days before attempting more contacts.
- April 02-03-04/09: Back in the saddle again. Worked 3 new initials on April 02 in less than 1/2 hour via JT65 mode. HB9HAL (JT #5) who was shaking the speaker at -8dB... loudest signal I've heard, VE7BBG (JT#6) and RW6AG (JT #7). The next day I worked HB9HAL (539) for my second CW inital and LA9NEA for JT65 intial #8. Worked G4CCH for CW inital #3 on April 4th. A good weekend overall !
- May 02/09: Worked K1RQG for a new initial and my first CW random ! Joe's signal was strong and easily copied, like listening to CW on HF. Also heard and called K2DH but no reply. Dave tells me that he listened to my QSO with K1RQG and could just barely hear me with my 75 watts. Should be an easy contact once I get the bigger amplifier online. K1RQG also reports that I was TXing 3.5kHz low. Also had trouble trying to work PY2BS in JT65C. I had consistent decodes from Bruce but he could not find me. My current setup uses a DB6NT transverter on RX and the TS-2000x on TX. Both are off frequency in the opposite direction so a good alignment is in order.
- May 12/09: Checked frequency of my TS-2000X transceiver using a R&S FSEA spectrum analyzer which is accurate to within a few Hz against my LPRO Rubidium Oscillator at 10 MHz. The TX was indeed a couple of kHz low so I re-aligned the master oscillator. Now within several tens of Hz on 23cm.
- May 15-17/09: Got down to Dayton for Hamvention weekend. The weather forecast was touch and go for rain but it held out and in fact turned out to be great ! Got a few great deals and bumped into several EME & weak signal guys.
- May 24/09: Worked PY2BS for JT65 inital #9. Bruce reported that he was hearing me on his TX frequency so all seems well ! Also worked Jan PA3FXB in JT65 for the 4th time. S/N was a bit low as the Moon was very close to the Sun (New Moon today).
- May 30-31/09: DUBUS/REF Contest. I operated for 2 hours on the 30th (Friday evening) and 4 hours on the 31st (Sunday evening) but missed Saturday due to a family wedding. Worked 4 stations in CW, 3 of which were new initials. K1RQG, K5JL for CW#5, OE9ERC for CW#6 and OZ4MM for CW#7. Near misses with K0YW and F2TU from whom I only got QRZ/YYY. At times the band sounded like 20 metres with lots of audible CW signals... it was great ! I also worked OE9ERC via JT65 for JT#10. I had a good time and it was a great opportunity to add more entries to the log.
--- QRT FOR THE SUMMER ---
My dish has been dismantled indefintely as I work through some other priorities. I plan to return in the future on 23cm with more power and a better aiming system. I'm also *slowly* building equipment to give 13cm EME a try. Hope to be back on in the near future !
Thanks to following people for their patience, encouragement and help in making my 23cm EME effort a success:
* Sam, G4DDK for sharing his small dish EME experience and his replies to my many e-mail inquiries.
* Barry, VE4MA for also responding to my many technical questions via e-mail.
* Dave, WW2R for posting details of his dish installation on his web page from which I borrowed some good ideas.
* Sven, SM5LE for his inspirational small dish EME web page and great showing of enginuity.
* My neighbor Harry for his cutting and welding efforts on pieces for the dish mount.
Useful 23cm EME Links:
K2UYH's 432 MHz and up Newsletter
G4DDK Sam's Web Site
WW2R/ G4FRE Dave's Web Site
SM5LE Sven's Web Site
Polar Mounts, well explained by W4OP
OE5JFL's 23cm EME Beacon
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